Cellulose is a polymer of glucose linked by β-1,4-glucosidic bonds. Cellulose chains form numerous intra- and intermolecular hydrogen bonds, which result in the formation of insoluble cellulose microfibrils. Microbial hydrolysis of cellulose to glucose involves the following three major classes of cellulases: (i) endoglucanases (EC 3.2.1.4) which cleave β-1,4-glucosidic links randomly throughout cellulose molecules; (ii) cellobiohydrolases (EC 3.2.1.91) which digest cellulose from the nonreducing end, releasing cellobiose; and (iii) β-glucosidases (EC 3.2.1.21) which hydrolyse cellobiose and low-molecular-mass cellodextrins to release glucose.
Cellulases are produced by many microorganisms and are often present in multiple forms. Recognition of the economic significance of the enzymatic degradation of cellulose has promoted an extensive search for microbial cellulases which can be used industrially. As a result, the enzymatic properties and the primary structures of a large number of cellulase have been investigated. On the basis of the results of a hydrophobic cluster analysis of the amino acid sequence of the catalytic domain, these cellulases have been placed into different families of glycosyl hydrolases; fungal and bacterial glycosyl hydrolases have been grouped into 35 families (Henrissat et. al. (1991), (1993)). Most cellulases consist of a cellulose-binding domain (CBD) and a catalytic domain (CAD) separated by a linker which may be rich in proline and hydroxy amino residues. Another classification of cellulases has been established on the basis of the similarity of their CBDs (Gilkes et al. (1991)) giving five families of glycosyl hydrolases (I-V).
Cellulases are synthesized by a large number of microorganisms which include fungi, actinomycetes, myxobacteria and true bacteria but also by plants. Especially endo-β-1,4-glucanases of a wide variety of specificities have been identified. Many bacterial endoglucanases have been described (Henrissat (1993); Gilbert et al.,(1993)).
An important industrial use of cellulolytic enzymes is the use for treatment of paper pulp, e.g. for improving the drainage or for deinking of recycled paper. Another important industrial use of cellulolytic enzymes is the use for treatment of cellulosic textile or fabric, e.g. as ingredients in detergent compositions or fabric softener compositions, for bio-polishing of new fabric (garment finishing), and for obtaining a “stone-washed” look of cellulose-containing fabric, especially denim, and several methods for such treatment have been suggested, e.g. in GB-A-1 368 599, Ep-A-0 307 564 and Ep-A-0 435 876, WO 91/17243, WO 91/10732, WO 91/17244, PCT/DK95/000108 and PCT/DK95/00132.
There is an ever existing need for providing novel cellulase enzymes or enzyme preparations which may be used for applications where cellulase, preferably an endo-β-1,4-glucanase, activity (EC 3.2.1.4) is desirable.
The object of the present invention is to provide novel enzymes and enzyme compositions having substantial cellulolytic activity under slightly acidic to alkaline conditions and improved performance in paper pulp processing, textile treatment, laundry processes, extraction processes or in animal feed; preferably such novel well-performing endoglucanases are producible or produced by using recombinant techniques in high yields.